Powertrain Control Module (PCM)

WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The PCM determines the desired torque requirements by driver demand (accelerator pedal and brake pedal). The PCM then determines what portion of the torque the engine delivers. The PCM commands the engine to create the correct amount of torque based on the following criteria: spark, throttle, and fuel delivery.

The PCM determines the generator mode based on the operating mode. The PCM broadcasts a controller area network (CAN) message indicating the desired generator mode. The available generator modes are Torque Mode, Speed, Engine Start (cold start, high-speed start and normal start) or Engine Stop. Typically, the engine operates in torque mode while the generator operates in speed mode (exception: dual electric launch).

The PCM calculates the gear mode based on the following inputs: transmission range sensor position and vehicle speed. Gear mode may be in one of the following states: PARK, REVERSE, NEUTRAL, DRIVE, or LOW.

The PCM determines when the engine is started or stopped. The PCM then coordinates the start or stop event with the transaxle control module (TCM). The PCM determines when the engine runs. The PCM uses the following criteria to determine when the engine starts: desired torque to be delivered from the powertrain, high voltage traction battery charge level, engine system temperatures, and climate control conditions (heater or A/C demands).

The PCM also commands the engine to start the first time that the key is rotated to the START position during a power up event. The PCM allows the engine to be restarted any time the key is rotated to the START position. The PCM monitors the length of time that the engine has been off and may delay the start of the engine to prevent the customer perception that the engine is cycling on and off too often.

The PCM determines when the engine stops. The PCM uses the following criteria to determine when the engine stops: desired torque to be delivered from the powertrain, high voltage battery charge level, climate control conditions (heater or A/C demands), and engine temperature. The PCM monitors the length of time that the engine has run and may command the engine to remain running to maintain a minimum engine run time, to prevent the customer perception that the engine is cycling on and off too often. To coordinate the start of the engine, the PCM uses engine speed, engine running flag, and exhaust heated flag. The outputs from the PCM include: desired engine torque, desired engine speed, operating mode, engine mode, and generator mode. To coordinate the stopping of the engine, the PCM uses engine speed, and engine running flag. The outputs from the PCM include: desired engine torque, desired engine speed, operating mode, engine mode, and generator mode.

The PCM calculates the regenerative braking torque limit. The PCM considers the following information in order to calculate the limit: charge current maximum, generator torque, generator speed, engine torque, engine speed, motor torque, motor speed, battery voltage, and the maximum inverter voltage.

The PCM is on the high speed CAN. If 1 of the 2 bus wires becomes shorted to ground or voltage, communications of the CAN network may not be possible. If there is an open in the network, communications may continue between some modules depending upon the location of the open circuit. Check the high speed CAN circuits 1908 (WH) and 1909 (BK) between the PCM C175b and the data link connector (DLC) C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the high speed CAN, damage to the DLC C251, damage to the PCM C175b, or a problem in the in-line connector. Since both the PCM and the traction battery control module (TBCM) share network termination responsibilities, a problem in either of these modules can result in a high speed CAN failure. For additional PCM information, refer to the INTRODUCTION - HYBRID article. For removal and installation information, refer to ELECTRONIC ENGINE CONTROLS - HYBRID .